Cacti that grow on trees

There
are cacti which grow in rainforests. Conditions here are completely different,
so these plants look very different.

You may not believe it, but this is a cactus growing on a tree.

A plant which grows on another plant is called an epiphyte. This is an
epiphytic cactus called Rhipsalis, and there
are many other epiphytic cacti, including the well-known and popular Christmas
cactus.

Epiphytic cacti are not parasites. An epiphyte uses another plant or tree
for support but does not take nutrients from it. A parasite will take its
nourishment from its host tree, and will often kill it.

Little pockets of humus, formed by rotting leaves, collect in hollows and
crevices in the tree bark and epiphytic cacti root in these. They also have
aerial roots, which absorb water from the moist air.

Some
epiphytic cacti have the most amazing flowers.

This is an Epiphyllum. You can see from the picture that it has broad,
flat stems that look like leaves.

The beautiful white flowers can be as much as 20cms across. They open at
night and are sweetly scented.